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Re: Is time an illusion?

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On 2017-09-26 21:59, Eric Douglas wrote:
> On Monday, September 25, 2017 at 4:31:11 PM UTC-4, Daniele Futtorovic wrote:
>> Cheers,
>>
>> I'm trying to synchronise a process between two machines (actual, not
>> virtual). I require sub-millisecond precision.
>>
>> I initialise clocks backed by System#nanoTime() on each end and
>> synchronise them somehow (there'll be some deviation at this point.
>> Doesn't matter). Subsequently, I time my process on each end relative to
>> this starting point.
>>
>> I have the impression that I'm seeing time drift in this process.
>> Disregarding measurement errors, the differences between the clocks seem
>> to increase over time.
>>
>> Q: Is this to be expected? I've been trying to read up on it a bit
>> (Oracle memory-holing all the sun.com blogs doesn't help), but wanted
>> some confirmation: is time really an illusion? Are 10^9 nanoseconds on
>> box A possibly not 10^9 nanoseconds on box B?
>>
>> If so, seriously, what the heck? I'm aware I might have stumbled on a
>> very elementary truth here after so many years in the business, but I
>> must say, the idea itself feels deeply unsettling.
>>
>> Existential musings aside, would any of you have suggestions as to how
>> tackle the issue?
>>
> First, have you read about time?
> https://en.wikipedia.org/wiki/System_time

I hadn't, but now that I have, I'm not sure what it would have changed.
Unless I've missed something, that article doesn't seem to mention the
central fact that CPUs cannot deterministically measure time (whatever
time is).

> Second, are the 2 machines physically beside each other?  That does make a difference in measuring real Earth time.
> https://en.wikipedia.org/wiki/Gravitational_time_dilation

All right, but that's not relativity that's at work here, is it? That
article for instance mentions differences in the trillionth for clocks
set a couple of kilometres apart; we're talking about differences in the
thousandth or ten-thousandth for boxes standing in the same room.

As others have weighed in, voltage fluctuations (and perhaps material
imperfections?) seem to be a perfectly reasonable -- if unsettling --
explanation, and those aren't due to relativity, are they?

-- 
DF.

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Thread

Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-25 22:30 +0200
  Re: Is time an illusion? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-09-25 18:02 -0400
    Re: Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-26 00:16 +0200
      Re: Is time an illusion? Jerry Stuckle <jstucklex@attglobal.net> - 2017-09-25 19:18 -0400
      Re: Is time an illusion? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-09-26 15:37 -0400
        Re: Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-27 01:13 +0200
          Re: Is time an illusion? Jerry Stuckle <jstucklex@attglobal.net> - 2017-09-26 21:00 -0400
            Re: Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-27 04:26 +0200
              Re: Is time an illusion? Jerry Stuckle <jstucklex@attglobal.net> - 2017-09-26 23:32 -0400
                Re: Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-28 10:58 +0200
                Re: Is time an illusion? Jerry Stuckle <jstucklex@attglobal.net> - 2017-09-28 12:50 -0400
            Re: Is time an illusion? Eric Douglas <e.d.programmer@gmail.com> - 2017-09-27 05:25 -0700
            Re: Is time an illusion? Arne Vajhøj <arne@vajhoej.dk> - 2017-09-30 22:57 -0400
  Re: Is time an illusion? Arne Vajhøj <arne@vajhoej.dk> - 2017-09-25 20:22 -0400
  Re: Is time an illusion? Marcel Mueller <news.5.maazl@spamgourmet.org> - 2017-09-26 20:18 +0200
    Re: Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-27 01:30 +0200
      Re: Is time an illusion? lewbloch@gmail.com - 2017-09-28 10:52 -0700
  Re: Is time an illusion? Eric Douglas <e.d.programmer@gmail.com> - 2017-09-26 12:59 -0700
    Re: Is time an illusion? Daniele Futtorovic <da.futt.news@laposte.net> - 2017-09-27 01:42 +0200
  Re: Is time an illusion? lewbloch@gmail.com - 2017-09-28 10:49 -0700
    Re: Is time an illusion? Robert Klemme <shortcutter@googlemail.com> - 2017-09-28 22:33 +0200

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